Process measurement instrument adapted for wireless communication

• US 20080278145A1
• Filed: 05/07/2007
• Published: 11/13/2008
• Est. Priority Date: 05/07/2007
• Status: Active Grant

• Current Assignee: Rosemount Tank Radar AB (Emerson Electric Company)
• Original Assignee: Rosemount Tank Radar AB (Emerson Electric Company)
• Inventors: Wenger, Fabian
• Granted Patent: US 8,447,367 B2
• Time in Patent Office: Days
• US Class Current: 324/157
• CPC Class Codes: G01F 23/284 Electromagnetic waves
• CPC Class Codes: G08C 17/04 using magnetically coupled devices
• CPC Class Codes: H04Q 2209/43 using wireless personal area networks [WPAN], e.g. 802.15, 802.15.1, 802.15.4, Bluetooth or ZigBee
• CPC Class Codes: H04Q 2209/883 where the sensing device enters an active or inactive mode
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

A process measurement instrument adapted for wireless communication, comprising a measurement unit (7) arranged to determine a measurement value of a process variable, a memory (21) arranged to store a current measurement value of the process variable, a wireless communication unit (8), arranged to access the current measurement value and communicate the current measurement value over a wireless communication channel according to a protocol with intermittently active communication, and arbitration logic (22), in communication with the measurement unit and the wireless communication unit, and arranged to ensure that active periods of the measurement unit occur when the wireless communication is inactive.

The measurement unit and communication unit are thus able to share information via the common memory, e.g. by sequential read/write access. This avoids the need for simultaneous activity. The invention can be especially advantageous when the instrument is powered by an internal power store, such as a battery, and extend the lifetime of such a power store.

Claims

1. A process measurement instrument adapted for wireless communication, comprising:

a measurement unit arranged to determine a measurement value of a process variable, said measurement unit having an operation comprising active time periods and inactive time periods, said active time periods having higher power consumption than said inactive time periods,

a memory arranged to store a current measurement value of said process variable,

a wireless communication unit, arranged to access said current measurement value and communicate said current measurement value over a wireless communication channel according to a protocol with intermittently active communication, and

arbitration logic, in communication with said measurement unit and said wireless communication unit, and arranged to ensure that active periods of said measurement unit occur when said wireless communication is inactive.

2. A process measurement instrument according to claim 1, wherein said arbitration logic is arranged to prolong an inactive period of said measurement unit, so as to delay a subsequent active period until the wireless communication unit is inactive.

3. A process measurement instrument according to claim 1, wherein a measurement cycle of said measurement unit is divided over several active periods.

4. A process measurement instrument according to claim 1, wherein said instrument further comprises an internal power store.

5. A process measurement instrument according to claim 1, wherein said instrument further comprises a wireless interface for power supply.

6. A process measurement instrument according to claim 1, wherein said measurement unit comprises a transceiver for transmission of electromagnetic waves during said active periods.

7. A process measurement instrument according to claim 1, arranged to determine the level of a product in a tank, comprising:

a transceiver for transmitting and receiving electromagnetic signals,

a propagation device arranged to allow a transmitted signal to propagate towards said surface, and to return a reflected signal to the transceiver, and

processing circuitry for determining said measurement value based on a relationship between said transmitted signal and said received signal.

8. A process measurement instrument according to claim 1, wherein said communication protocol is a time division multiple access (TDMA) protocol.

9. A method for communicating a measurement value of a process variable from a measurement unit arranged to determine said measurement value, said measurement unit having an operation comprising active time periods and inactive time periods said active time periods having higher power consumption than said inactive time periods, said method comprising the steps of:

storing a current measurement value of said process variable,

accessing a stored current measurement value, communicating said current measurement value over a wireless communication channel according to a protocol with intermittently active communication, and

controlling said measurement unit and said wireless communication to ensure that active periods of said measurement unit occur when said wireless communication is inactive.

10. The method according to claim 9, wherein said step of controlling comprises prolonging an inactive period of said measurement unit, so as to delay a subsequent active period until the wireless communication unit is inactive.

11. The method according to claim 9, wherein a measurement cycle of said measurement unit is divided over several active periods.

12. The method according to claim 9, wherein said communication protocol is a time division multiple access (TDMA) protocol.

101-112. -112. (canceled)